Improved rotor position estimation in extended back-EMF based sensorless PM brushless AC drives with magnetic saliency

Abstract

An improved extended back-EMF based sensorless control method is proposed for a brushless AC motor equipped with an interior permanent magnet rotor. It accounts for dq-axis cross-coupling magnetic saturation by introducing an apparent mutual winding inductance. The error which results in the estimated rotor position when the influence of cross-coupling magnetic saturation is neglected is analyzed analytically, predicted by finite element analysis, and confirmed experimentally, for various d- and q-axis currents. It is shown that a significant improvement in the accuracy of the rotor position estimation can be achieved by the proposed method, as confirmed by measurements